1. Field of the Invention
The present invention relates to an electronic blur correction device and an electronic blur correction method capable of effectively compensating for image blur caused by hand shake and the like. Particularly, the present invention relates to an electronic blur correction device and an electronic blur correction method for compensating for mutual blurring of a plurality of images continuously shot at a blur tolerable exposure time and combining the images for which blur is corrected.
2. Description of the Related Art
It is conventionally known that blur may occur in a shot image due to the influence of photographer's hand movements upon shooting a still image with an imaging apparatus. Therefore, various measures have been taken to prevent this blur problem. For example, Japanese Patent Application Laid-Open No. 11-252445 discloses a technique for reading a plurality of images continuously from an image pickup device to compensate for mutual blurring of the plurality of images and combine the images in order to generate an image for which blur is corrected. In this Japanese Patent Application Laid-Open No. 11-252445, picture signals taken during periods of blur tolerable exposure time (period which time-length is so short that the amount of blur is negligible or allowable) are read from the image pickup device on a frame basis, and when the signal level of the picture signals exceeds a predetermined value, the shooting operation is terminated. During this shooting operation, motion vectors are detected from images and the images are superimposed onto each other to obtain a blur-corrected image.
In the blur correction technique disclosed in Japanese Patent Application Laid-Open No. 11-252445, when an accumulated value of the picture signals, each of which is taken during a period of fixed time-division exposure time, exceeds a predetermined value, the time-division exposure is completed. Therefore, in order to obtain the optimum exposure, the number of imaging times needs to be determined up to required digits after the decimal point and the imaging needs to be performed the determined number of times. In other words, when the optimum exposure time is set as Texp and the blur tolerable time-division exposure time is set as TLimit, a time-division image capturing of TLimit exposure time should be performed the number of times, m, where m=Texp/TLimit. And these images captured during the periods of the time-division exposure time are compensated for mutual image blurring and combined together, thereby making it possible to obtain an image without blur at the optimum exposure level.
However, the number of exposure times, m, is not an integer in the majority of cases. In such cases, when the fractional part of m is represented as k, the imaging for the exposure time TLimit needs to be performed (m−k) times and once for exposure time k×TLimit. After that, these images are compensated for mutual blurring and combined (added) together.